Competitive reactions in solutions of DNA-containing polyelectrolyte complexes

The reaction of competitive binding of two polyanions - DNA and synthetic fluorescence-tagged poly(methacrylate) (PMA*) - with the quencher polycation poly(N-ethyl-4-vinylpyridinium) (PEVP) was studied by fluorescence quenching technique. It is found that ability of DNA to displace PMA* from water-soluble nonstoichiometric interpolyelectrolyte complex (NPEC) formed by PMA* and PEVP - NPEC(PMA*-PEVP)- and to form water-soluble NPEC(DNA-PEVP) NPEC(PMA*-PEVP) + DNA double left right arrow NPEC(DNA-PEVP) + PMA* can be determined by both a parameter psi = P-PMA*/P-PEVP, where P-PMA* and P-PEVP are the degrees of polymerization of PMA* and PEVP, respectively, and by the nature and concentration of alkali and alkali earth metal cations. According to their ability to shift the equilibrium to the right the cations can be arranged in the series Ca2+ > Mg2+ >> Na+ > K+ > Li+. The data obtained are in accordance with the differences in the selectivity of alkali and alkali earth cations binding with competitive polyanions.